US7759622B2 - Methods and apparatus for regulating the drive currents of a plurality of light emitters - Google Patents
Methods and apparatus for regulating the drive currents of a plurality of light emitters Download PDFInfo
- Publication number
- US7759622B2 US7759622B2 US10/938,998 US93899804A US7759622B2 US 7759622 B2 US7759622 B2 US 7759622B2 US 93899804 A US93899804 A US 93899804A US 7759622 B2 US7759622 B2 US 7759622B2
- Authority
- US
- United States
- Prior art keywords
- light emitters
- drive currents
- modulation sequence
- light
- emitters
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related, expires
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Classifications
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
- H05B45/20—Controlling the colour of the light
- H05B45/22—Controlling the colour of the light using optical feedback
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F21—LIGHTING
- F21V—FUNCTIONAL FEATURES OR DETAILS OF LIGHTING DEVICES OR SYSTEMS THEREOF; STRUCTURAL COMBINATIONS OF LIGHTING DEVICES WITH OTHER ARTICLES, NOT OTHERWISE PROVIDED FOR
- F21V23/00—Arrangement of electric circuit elements in or on lighting devices
- F21V23/04—Arrangement of electric circuit elements in or on lighting devices the elements being switches
- F21V23/0442—Arrangement of electric circuit elements in or on lighting devices the elements being switches activated by means of a sensor, e.g. motion or photodetectors
- F21V23/0457—Arrangement of electric circuit elements in or on lighting devices the elements being switches activated by means of a sensor, e.g. motion or photodetectors the sensor sensing the operating status of the lighting device, e.g. to detect failure of a light source or to provide feedback to the device
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B47/00—Circuit arrangements for operating light sources in general, i.e. where the type of light source is not relevant
- H05B47/10—Controlling the light source
- H05B47/175—Controlling the light source by remote control
- H05B47/18—Controlling the light source by remote control via data-bus transmission
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B47/00—Circuit arrangements for operating light sources in general, i.e. where the type of light source is not relevant
- H05B47/10—Controlling the light source
- H05B47/175—Controlling the light source by remote control
- H05B47/19—Controlling the light source by remote control via wireless transmission
Definitions
- Devices capable of producing light of different wavelengths have allowed the construction of illumination and display devices capable of producing light of varied spectral content.
- the intensity of such a device may be controlled by changing the intensities of the device's individual emitters, and the spectral content of light produced by such a device may be controlled by changing the ratios of intensities of the device's different wavelength emitters.
- a method comprises modulating ones of a plurality of drive currents in accordance with a plurality of unique modulation sequences.
- the modulated drive currents are then applied to a plurality of light emitters.
- a stream of optical measurements is obtained from a photosensor that is positioned to sense the aggregate light emitted by the light emitters.
- the stream of optical measurements is then correlated with the unique modulation sequences to extract optical responses to each of the plurality of drive currents.
- each drive current is regulated based on its relationship to its corresponding optical response.
- apparatus comprises a plurality of light emitters, a photosensor, and a control system.
- the photosensor is positioned to sense the aggregate light emitted by the light emitters.
- the control system 1) modulates ones of a plurality of drive currents in accordance with a plurality of unique modulation sequences, 2) applies the modulated drive currents to the light emitters, 3) correlates a stream of optical measurements taken by the photosensor with the unique modulation sequences to extract optical responses to each of the plurality of drive currents, and 4) regulates each drive current based on its relationship to its corresponding optical response.
- apparatus comprises a plurality of light emitters, a photosensor, and a control system.
- the photosensor is positioned to sense the aggregate light emitted by the light emitters.
- the control system 1) applies a plurality of drive currents to the light emitters, 2) periodically alters one of the drive currents by a predetermined amount for a predetermined time, 3) for each drive current alteration, obtains readings from the photosensor with and without the drive current alteration, and 4) regulates each drive current based on its relationship to its corresponding photosensor readings.
- FIG. 1 illustrates a first exemplary method for regulating the drive currents of a plurality of light emitters
- FIG. 2 illustrates a second exemplary method for regulating the drive currents of a plurality of light emitters
- FIG. 3 illustrates exemplary apparatus for implementing the method shown in FIG. 1 or FIG. 2 .
- drifts in emitter intensities can result in changes in light intensity across the illumination device.
- drifts in emitter intensities can result in both 1) changes in light intensity across the device, as well as 2) changes in spectral content across the device.
- drifts in individual emitter intensities can result in image artifacts superimposed on the desired image.
- illumination and display devices comprised of solid-state light emitters (e.g., LEDs).
- solid-state light emitters e.g., LEDs
- the principles disclosed below are also applicable to other types of light emitters (e.g., gas discharge lamps).
- One way to control the intensities of light emitters in an illumination or display device is to use a different photosensor to sense the light produced by each of the device's emitters.
- this can become unwieldy and costly as the number of light emitters increases.
- it is often difficult to position a photosensor so that it only senses the light produced by a single emitter.
- a single photosensor (or single group of photosensors for measuring different wavelengths of light) is used to measure the aggregate light output (i.e., intensity) of a plurality of light emitters. Adjustments to the intensities of the light emitters are then made on a group basis. So long as all of the light emitters in the group are manufactured within close tolerances, and so long as all of the emitters respond to temperature changes, age and other factors in a similar manner, adjusting the spectral content of the light emitters on a group basis may be effective. However, if the light output to drive current relationships of two or more nominally identical emitters exhibit marked differences, then group control of the emitters results in substandard operation of the illumination or display device of which the emitters form a part.
- individualized controls for each of a plurality of light emitters may be derived from the sensor's output by periodically turning off one of the emitters while continuing to monitor the aggregate light output of the emitters.
- the contribution of the affected emitter can be computed.
- this has the effect of causing an abrupt change in the aggregate light output of the device, and can cause a visible flicker in the light output of the device. This flicker may be especially noticeable in small to moderate size arrays of light emitters.
- periodically removing one of its emitters from normal operation may appear as an unacceptable image defect.
- One way to reduce the flicker caused by turning a light emitter off and on is to temporarily increase the light output of the emitter immediately before and after it is turned off. Flicker is reduced because a human eye tends to average short periods of increased and no light output.
- the emitter usually has to be capable of producing substantially more than its nominal light output. This can lead to lower power efficiency and emitter overdesign. Without overdesign, the periodic substantial increase in emitter light output can lead to premature emitter aging, or even failure.
- FIGS. 1-3 illustrate new methods and apparatus for regulating the drive currents of a plurality of solid-state light emitters.
- the light output (L) of a solid-state light emitter is generally related to its drive current (I).
- I drive current
- an emitter's L/I relationship can sometimes change.
- a portion of an emitter's L/I relationship that is especially useful in characterizing the operation of the emitter is its dynamic L/I relationship, or the derivative of the emitter's L/I transfer curve about its nominal operating current. Temperature, aging and other effects cause the slope of the L/I curve to vary, and hence an assessment of an emitter's dynamic L/I relationship can be used to estimate its operating characteristics.
- FIG. 1 illustrates a first exemplary method 100 for regulating the drive currents of a plurality of solid-state light emitters.
- a plurality of drive currents is applied 102 to a plurality of light emitters.
- each drive current is applied to a different one of the light emitters.
- each drive current is applied to a subset of the light emitters.
- one of the drive currents is altered 104 (e.g., reduced or increased) by a predetermined amount (e.g., 2% of the drive current's nominal operating value) for a predetermined time.
- the alterations in drive currents may be undertaken on a rotating or random basis amongst the different drive currents.
- readings with and without the drive current alteration are obtained 106 from a photosensor that is positioned to sense the aggregate light emitted by the light emitters.
- aggregate light is a mixed light that is influenced by each of a plurality of light emitters.
- aggregate light need not always comprise all of the light emitted by the plurality of light emitters.
- the method 100 then continues with the regulation 108 of each drive current based on its relationship to its corresponding photosensor readings.
- this regulation may be performed in response to a calculation of an emitter's dynamic impedance about its nominal operating current.
- the emitter's dynamic impedance need not be calculated, and the emitter's drive current and photosensor readings may simply be used to look up a drive current or drive current adjustment.
- FIG. 3 shows an exemplary illumination device, display device or portion of a display device 300 in which the method 100 may be implemented.
- the device 300 comprises a plurality of solid-state light emitters 302 - 318 , and a photosensor 320 that is positioned to sense the aggregate light that is emitted by the light emitters 302 - 318 .
- the emitters 302 - 318 may emit light of different wavelengths (e.g., red (R), green (G) and blue (B) light).
- the emitters 302 - 318 could alternately emit light of more or fewer wavelengths, and could even emit a monochromatic light.
- the method 100 can only be used to ensure a uniform intensity of the emitters across the device 300 (i.e., since the spectral content of the device would be fixed by the device's monochromatic emitters).
- the device 300 further comprises a control system 322 .
- the control system 322 implements the method 100 , and possibly other control functions for the device 300 .
- the control system 322 is shown to be a single unit, the electronics of the control system 322 could alternately be distributed amongst various subsystems of the device 300 .
- FIG. 2 illustrates a second exemplary method 200 for regulating the drive currents of a plurality of solid-state light emitters.
- ones of a plurality of drive currents are modulated 202 in accordance with a pilot tone modulated by ones of a plurality of unique modulation sequences.
- the unique modulation sequences are orthogonal to one another, such that a cross-correlation of the modulation sequences is zero, and only the auto-correlation of a modulation sequence is non-zero.
- the method 200 continues with the application 204 of the modulated drive currents to a plurality of light emitters.
- each drive current is applied to a different one of the light emitters.
- each drive current is applied to a subset of the light emitters.
- a stream of optical measurements is obtained 206 from a photosensor that is positioned to sense the aggregate light emitted by the light emitters.
- the stream of optical measurements is then correlated 208 with the unique modulation sequences to extract optical responses to each of the plurality of drive currents. During correlation, optical measurements that do not correlate with a particular modulation sequence are perceived as aggregate “noise” and are ignored.
- each of the drive currents is regulated 210 based on its relationship to its corresponding optical response. In some cases, this regulation may be performed in response to a calculation of an emitter's dynamic impedance about its nominal operating current. In other cases, the emitter's dynamic impedance need not be calculated, and the emitter's drive current and optical response may simply be used to look up a drive current or drive current adjustment.
- the unique modulation sequences are based on pseudo-random bit sequences (PRBSs) that all have a mean of a nominal value and periodically repeat.
- PRBSs pseudo-random bit sequences
- the PRBS sequences may be Haddamarand-Walsh sequences or Gold sequences.
- the amplitudes of the PRBS modulation sequences can be quite small, as the correlation of a response with a PRBS sequence typically provides a high coding gain.
- the unique modulation sequences may be applied to their corresponding drive currents by modulating the drive currents with a pilot tone that, for each drive current, is modulated by a different one of the unique sequences.
- the pilot tone need not be used.
- the detected signal after correlation typically comprises a DC value, the magnitude of which is more difficult to determine than the amplitude of a pilot tone.
- the pilot tone may be a periodic signal such as a low amplitude square wave or sine wave.
- the pilot tone in combination with each unique modulation sequence, has an amplitude that is within two percent (2%) of the nominal operating value of the drive current to which it is applied.
- the method 200 may also be implemented in the illumination or display device 300 shown in FIG. 3 .
- the control system 322 may receive a stream of optical measurements from the photosensor 320 and extract optical responses from the stream in a serial fashion (i.e., by correlating a first modulation sequence with a first portion of the stream, by correlating a second modulation sequence with a second portion of the stream, and so on).
- the control system 322 extracts optical responses in parallel (e.g., by splitting or saving the stream of optical measurements received from the photosensor 320 ).
- the method 300 can be used on a continuous basis, with little or no visual impact on an illumination or display device 300 .
- the device 300 may serve as a backlight for a liquid crystal display (LCD).
- the device 300 may serve as general-purpose or special-purpose lighting (e.g., mood lighting or a cosmetics mirror light).
- the device 300 may form part or all of a display.
Abstract
Description
Claims (20)
Priority Applications (6)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US10/938,998 US7759622B2 (en) | 2004-09-10 | 2004-09-10 | Methods and apparatus for regulating the drive currents of a plurality of light emitters |
TW094118293A TW200623196A (en) | 2004-09-10 | 2005-06-03 | Methods and apparatus for regulating the drive currents of a plurality of light emitters |
CN2005100775434A CN1746948B (en) | 2004-09-10 | 2005-06-17 | Method and apparatus for regulating the drive currents of a plurality of light emitters |
EP05013277A EP1635617A3 (en) | 2004-09-10 | 2005-06-20 | Methods and apparatus for regulating the drive currents of a plurality of light emitters |
KR1020050083565A KR20060051100A (en) | 2004-09-10 | 2005-09-08 | Method and apparatus for regulating the drive currents of a plurality of light emitters |
JP2005263188A JP2006079099A (en) | 2004-09-10 | 2005-09-12 | Method and apparatus for regulating drive current of a plurality of light emitters |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US10/938,998 US7759622B2 (en) | 2004-09-10 | 2004-09-10 | Methods and apparatus for regulating the drive currents of a plurality of light emitters |
Publications (2)
Publication Number | Publication Date |
---|---|
US20060054776A1 US20060054776A1 (en) | 2006-03-16 |
US7759622B2 true US7759622B2 (en) | 2010-07-20 |
Family
ID=35447493
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US10/938,998 Expired - Fee Related US7759622B2 (en) | 2004-09-10 | 2004-09-10 | Methods and apparatus for regulating the drive currents of a plurality of light emitters |
Country Status (6)
Country | Link |
---|---|
US (1) | US7759622B2 (en) |
EP (1) | EP1635617A3 (en) |
JP (1) | JP2006079099A (en) |
KR (1) | KR20060051100A (en) |
CN (1) | CN1746948B (en) |
TW (1) | TW200623196A (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20090015839A1 (en) * | 2007-07-11 | 2009-01-15 | Hitachi, Ltd. | Living body optical measurement system |
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EP2016807A4 (en) * | 2006-04-21 | 2011-02-16 | Koninkl Philips Electronics Nv | Method and apparatus for light intensity control |
US20080055896A1 (en) * | 2006-08-30 | 2008-03-06 | David Charles Feldmeier | Systems, devices, components and methods for controllably configuring the color of light emitted by an automotive LED illumination system |
US20080055065A1 (en) * | 2006-08-30 | 2008-03-06 | David Charles Feldmeier | Systems, devices, components and methods for controllably configuring the brightness of light emitted by an automotive LED illumination system |
ATE474439T1 (en) | 2006-10-27 | 2010-07-15 | Koninkl Philips Electronics Nv | COLOR-CONTROLLED LIGHT SOURCE AND METHOD FOR CONTROLLING COLOR GENERATION IN A LIGHT SOURCE |
US9179516B2 (en) | 2006-10-27 | 2015-11-03 | Koninklijke Philips N.V. | Color controlled light source and a method for controlling color generation in a light source |
US9414458B2 (en) | 2007-05-24 | 2016-08-09 | Federal Law Enforcement Development Services, Inc. | LED light control assembly and system |
US9100124B2 (en) | 2007-05-24 | 2015-08-04 | Federal Law Enforcement Development Services, Inc. | LED Light Fixture |
US11265082B2 (en) | 2007-05-24 | 2022-03-01 | Federal Law Enforcement Development Services, Inc. | LED light control assembly and system |
US9455783B2 (en) | 2013-05-06 | 2016-09-27 | Federal Law Enforcement Development Services, Inc. | Network security and variable pulse wave form with continuous communication |
WO2008148022A2 (en) * | 2007-05-24 | 2008-12-04 | Federal Law Enforcement Development Services, Inc. | Building illumination apparatus with integrated communications, security and energy management |
JP5441900B2 (en) | 2007-07-16 | 2014-03-12 | コーニンクレッカ フィリップス エヌ ヴェ | Driving the light source |
EP2177082B1 (en) * | 2007-08-07 | 2012-07-11 | Koninklijke Philips Electronics N.V. | Method and apparatus for discriminating modulated light in a mixed light system |
DE102007045259A1 (en) | 2007-09-21 | 2009-04-02 | Continental Automotive Gmbh | Method and device for detecting the light output emitted by an LED light source |
WO2009040705A2 (en) * | 2007-09-28 | 2009-04-02 | Koninklijke Philips Electronics N.V. | Method and apparatus for light intensity control with drive current modulation |
EP2328385A1 (en) * | 2008-01-17 | 2011-06-01 | Koninklijke Philips Electronics N.V. | Method and apparatus for light intensity control |
WO2009093191A2 (en) * | 2008-01-25 | 2009-07-30 | Koninklijke Philips Electronics N.V. | Lighting system comprising a light source, a controller and a light sensor |
US8890773B1 (en) | 2009-04-01 | 2014-11-18 | Federal Law Enforcement Development Services, Inc. | Visible light transceiver glasses |
US8258709B2 (en) | 2010-09-01 | 2012-09-04 | Osram Sylvania Inc. | LED control using modulation frequency detection techniques |
US8390205B2 (en) * | 2010-09-01 | 2013-03-05 | Osram Sylvania Inc. | LED control using modulation frequency detection techniques |
US8729815B2 (en) | 2012-03-12 | 2014-05-20 | Osram Sylvania Inc. | Current control system |
US20150198941A1 (en) | 2014-01-15 | 2015-07-16 | John C. Pederson | Cyber Life Electronic Networking and Commerce Operating Exchange |
US20170048953A1 (en) | 2015-08-11 | 2017-02-16 | Federal Law Enforcement Development Services, Inc. | Programmable switch and system |
DE102016205529A1 (en) * | 2016-04-04 | 2017-10-05 | Osram Gmbh | Method for measuring light |
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-
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- 2005-06-17 CN CN2005100775434A patent/CN1746948B/en not_active Expired - Fee Related
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Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20090015839A1 (en) * | 2007-07-11 | 2009-01-15 | Hitachi, Ltd. | Living body optical measurement system |
US8750951B2 (en) * | 2007-07-11 | 2014-06-10 | Hitachi, Ltd. | Living body optical measurement system |
Also Published As
Publication number | Publication date |
---|---|
KR20060051100A (en) | 2006-05-19 |
EP1635617A2 (en) | 2006-03-15 |
CN1746948A (en) | 2006-03-15 |
US20060054776A1 (en) | 2006-03-16 |
CN1746948B (en) | 2012-08-29 |
JP2006079099A (en) | 2006-03-23 |
TW200623196A (en) | 2006-07-01 |
EP1635617A3 (en) | 2008-01-16 |
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